The present invention relates to an apparatus for use in the manufacture of a semiconductor device, and more particularly, to a gas supplying apparatus for evenly supplying various gases to a reaction chamber.
The different manufacturing processes of a semiconductor device employ an assortment of apparatuses using various gases which are often toxic and/or reactive. Thus, an apparatus for performing such gas treatment processes requires numerous safety devices, especially for guarding against gas leaks. On the other hand, to manufacture reliable devices, the apparatus should precisely control the amount of gas flow, in addition to preventing the leakage of hazardous gases.
In an apparatus as above, the gas is supplied to the reaction chamber from a main gas reservoir via a main gas line and individual gas lines and is used for growing a film. Thus, it is important to keep the gas lines clean and ensure that the gases do not react with one another until being supplied to the reaction chamber, such that the reaction occurs only in the reaction chamber.
Among semiconductor processing apparatuses, a chemical vapor deposition (CVD) apparatus is widely used for growing many kinds of film. The CVD method is used for forming a thin film or an epitaxial layer on a semiconductor substrate by a chemical reaction after decomposing a compound in a vapor state. The CVD process is different from other semiconductor device manufacturing processes in that a thin layer can be formed by introducing a gas to a reaction chamber. Here, an effective CVD reaction occurs over a wide temperature range (about 100.degree.-1200.degree. C.), and plasma energy by radio frequency (RF) power, optical energy (e.g., a laser or ultraviolet light) and heat are used for decomposing the introduced gas. Also, the semiconductor substrate is heated to promote the reaction of the decomposed atom or molecule and to control the physical properties of the formed film.
Generally speaking, the CVD method is divided into an atmospheric pressure CVD (APCVD) method and a low pressure CVD (LPCVD) method, according to the degree of vacuum in the reaction chamber during the process.
Recently, CVD methods have been adopted extensively in the semiconductor industry due to certain distinct merits: (a) silicon epitaxial layers can be formed with the desired thicknesses and resistances, (b) polysilicon, silicon oxide and silicon nitride layers can be obtained at low cost, and (c) the silicon oxide and silicon nitride layers (for the protection of silicon devices) can be formed at relatively low temperatures.
A physicochemical characteristic of the thin layer obtained by the CVD method is determined by the construction of the substrate (e.g., amorphous, polycrystalline or crystal) on which a thin film is deposited and the deposition conditions (i.e., temperature, growing rate, pressure, etc.). Generally, the above variables affect the surface mobility of the deposited atoms, thereby determining the construction and other characteristics of the film.
Here, two CVD apparatuses and their gas supply methods (disclosed in Japanese Patent Applications Nos. 89-264258 and 92-7825) will be described. The conventional CVD apparatuses are shown in FIGS. 1 and 2.
First, FIG. 1 is a diagram schematically showing the construction of a CVD apparatus using plasma.
As shown in FIG. 1, the plasma CVD apparatus comprises a reaction chamber 12, a susceptor 14 disposed horizontally inside the reaction chamber, and a shower head 19. Here, a silicon substrate 13 is seated on the susceptor 14. Situated above reaction chamber 12, a first gas supply pipe 15 is connected to shower head 19 and a first mass flow controller 16 controls the amount of gas flowing in the first gas supply pipe. Also, a booster pump 11 and a rotary pump 10 are connected beneath reaction chamber 12 for controlling the pressure and drawing off the gas within the reaction chamber. Provided on one side of reaction chamber 12, an incubator 18 generates gas by evaporating the liquid in a liquid source 17, and a second gas supply pipe 20 introduces the gas from the liquid source, the amount of which is controlled by a second mass flow controller 21.
Next, FIG. 2 is a diagram schematically showing the constitution of the conventional LPCVD apparatus.
Referring to FIG. 2, the LPCVD apparatus comprises a reaction chamber 33, a susceptor 25 disposed horizontally inside the reaction chamber, a shower head 32, and a heating block 29 for heating a silicon substrate 28 seated on the susceptor. Situated above reaction chamber 33, a first gas supply pipe 34 is connected to shower head 32, and an RF generating apparatus 31 is connected to the first gas supply pipe. Also, a mass flow controller 27 controls the amount of gas flowing in the first gas supply pipe 34. A booster pump 24 and a rotary pump 23 are connected beneath reaction chamber 33 for controlling the pressure and drawing off the gas within the reaction chamber. Provided above and to the side of reaction chamber 33, an incubator 30 generates gas by evaporating the liquid in a liquid source 22, and a second gas supply pipe 26 introduces the gas from the liquid source.
As above, both ga supply methods of the conventional CVD apparatuses shown in FIGS. 1 and 2 prevent the gases from interacting before reaching the reaction chamber. The above methods are generally employed for the purpose of preventing particle generation or the clogging of the gas supply pipes; problems which are the result of the gases becoming mixed prematurely and thus reacting with each other outside the reaction chamber. In these methods, however, the gas is not distributed evenly inside the reaction chamber, and as a result, the uniformity of the film thickness grown on the substrate is adversely affected.